Cast Class object

Hi,
I would like to cast an object type Class to another type, eg. MyAdapterClass. I can not figure out any way of doing so, so help is highly appreciated...
Thanx, Flo!
ClassLoader cl = ClassLoader.getSystemClassLoader();
Class classTemp = cl.loadClas("MyAdapterClass");
// something similar to the line below is required..
// MyAdapterClass mac = (MyAdapterClass)classTemp;

Multi-post
http://forum.java.sun.com/thread.jspa?threadID=754736
@Op. Please don't create several threads with the same question.
Kaj

Similar Messages

Casting base class object to derived class object

interface myinterface
     void fun1();
class Base implements myinterface
     public void fun1()
class Derived extends Base
public class File1
     public myinterface fun()
          return (myinterface) new Base();
     public static void main(String args[])
          File1 obj = new File1();
          Derived dobj = (Derived)obj.fun();
Giving the exception ClassCastException......
Can't we convert from base class object to derived class.
Can any one help me please...
Thnaks in Advance
Bharath kumar.

When posting code, please use tags
The object returned by File1.fun() is of type Base. You cannot cast an object to something it isn't - in this case, Base isn't Dervied. If you added some member variables to Derived, and the compiler allowed your cast from Base to Derived to succeed, where would these member variables come from?
Also, you don't need the cast to myinterface in File1.fun()
Also, normal Java coding conventions recommend naming classes and interfaces (in this case, myinterface) with leading capital letters, and camel-case caps throughout (e.g. MyInterface)

Casting timezone class object to Simpletimezone class object

When i try to cast timezone class object to a simpletimezone object it throws "java.lang.classcastexception" when i use J2re 1.4.2_06 while in J2re1.3 it works fine .
I am unable to understand this , can anybody help me out in this regard.
thanks
Lokesh

I agree with all
but try this out
SimpleTimeZone stz = (SimpleTimeZone)
ne) TimeZone.getTimeZone(id);Nothing in the specification says that
TimeZone.getTimeZone(id) returns an object that is a
SimpleTimeZone only that it is a TimeZone. It might
happen to also be a SimpleTimeZone but nothing in the
specifications says that it is.
Above statement throws classcast exception in
in jre1.4.2 but not in Jre1.3 and lower versions
........ remember TimeZone is base class and
SimpleTimeZone is sub class.If this is correct then in 1.3 it just happens to
return SimpleTimeZone object but nothing in the spec
says you can rely on this. You are relying on an
undocumented feature! Always a bad idea.
So wht has changed in the 2 runtimeenvironments.
Retorical?Hi,
sabre150 thanx a lot , u are right in earlier versions TimeZone.getTimeZone(id) was returning SimpleTimeZone object but in J2re 1.4.2 it returns sun.util.calendar.ZoneInfo object and hence the class cast exception was happening.
AND BELLYRIPPER , u were theoretically right , i was asking something that was happening in practical , so u better try out things and then come up with reasoning rather than just repeating theoretical things and expecting others to accept them blindly.
Anyway thanx a lot for the help.

How to cast an Object into a specific type (Integer/String) at runtime

Problem:
How to cast an Object into a specific type (Integer/String) at runtime, where type is not known at compile time.
Example:
public class TestCode {
     public static Object func1()
Integer i = new Integer(10); //or String str = new String("abc");
Object temp= i; //or Object temp= str;
return temp;
     public static void func2(Integer param1)
          //Performing some stuff
     public static void main(String args[])
     Object obj = func1();
//cast obj into Integer at run time
     func2(Integer);
Description:
In example, func1() will be called first which will return an object. Returned object refer to an Integer object or an String object. Now at run time, I want to cast this object to the class its referring to (Integer or String).
For e.g., if returned object is referring to Integer then cast that object into Integer and call func2() by passing Integer object.

GDS123 wrote:
Problem:
How to cast an Object into a specific type (Integer/String) at runtime, where type is not known at compile time.
There is only one way to have an object of an unknown type at compile time. That is to create the object's class at runtime using a classloader. Typically a URLClassloader.
Look into
Class.ForName(String)

Please help how to set/get a class object in hashtable or hashmap?

Hi, everybody.
I'd like to generate a class-object list in hashtable.
However, compilation is error. Here is my code:
Hashtable ht = new Hashtable();
Class tmp_obj;
tmp_obj = Class.forName("my_class_name_1");
ht.put("my_class_name_1", tmp_obj);
tmp_obj = Class.forName("my_class_name_2");
ht.put("my_class_name_2", tmp_obj);
Class selected_object = ht.get("my_class_name");
^here compilation error: incompitable types
Could anybody tell me where is wrong in my code and how to
correct it?
Thank you in advance.
Jeff

Look at the javadoc for Hashtable. The get method returns an Object. You will need to cast it to a Class object.
Class selected_object = (Class)ht.get( "my_class_name" );If you are using JDK5.0, then you should look up generics.

Putting a Class Object into a Vector

HI all
I need to put a class object into another classes vector, then be able to read it and retrieve data.
I can put the object into the vector but all i seem to be able to retrieve is data like Account@2343c2.
Is this some sort of tag? How do i get to the data?
thankz
joey

That's what you get when you print an object which does not have its own toString() method to do anything different - it picks up the Object class's toString method instead. For example:
System.out.println(new Object());It sounds like you're doing something like this:
Vector v = new Vector();
v.add(new Account(42));If you were to do the following, you would see that sort of output:
System.out.println(v.get(0));The appropriate way to do this would be something like the following:
   // Use a List reference instead of a Vector reference, and create
   // an ArrayList object in preference to a Vector object
   List list = new ArrayList();
   list.add(new Account(42));
   // Iterate through the list of accounts - use an
   // iterator because this prevents off-by-one errors
   // that arise with direct indexing.
   Iterator i = list.iterator();
   while(i.hasNext()) {
      // Cast the reference returned by the iterator from
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      // methods.
      Account current = (Account)i.next();
      // Call the method specific to the Account class (getBalance
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      System.out.println(current.getBalance());
   }

EJB3 Stateful:ClassCastException when casting the object returned in lookup

Hi,
I'm developing a web application that make use of EJB3 stateless and stateful beans. The application server is the Websphere Application Server 6.1.0.15 with the EJB3 Feature Pack installed and the web server is the IBM HTTP Server running in another machine.
The problem I'm facing is that for every stateful bean after the lookup, it throws a ClassCastExcption when casting the object returned. See part of the log below.
[7/13/08 3:15:48:869 CDT] 0000001c SystemErr R java.lang.ClassCastException: cannot cast class com.spcs.dsa.ejb.authenticationmanager._AuthenticationManager_Stub to class com.spcs.dsa.ejb.authenticationmanager._AuthenticationManager_Stub
at com.ibm.rmi.javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:396)
at com.spcs.dsa.ejb.client.DsaEjbClient.getAuthenticationRemote(DsaEjbClient.java:37)
at com.spcs.dsa.action.NewCardAction.execute(NewCardAction.java:85)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
Please notice in the log above that the cast was done for the correct class.
Here is the java code:
AuthenticationManager auth =
(AuthenticationManager) javax.rmi.PortableRemoteObject.narrow(
context.lookup("com.spcs.dsa.ejb.authenticationmanager.AuthenticationManager"),
AuthenticationManagerStub.class);
This problem doesn't happen for statless beans. If you simply change the class to be stateless, this problem stop to happen.
If you run this code in a stand alone program, this problem doesn't happen. It only happen when running in the web server.
Does anybody know what should be done to solve this problem ??
Thanks,
Marcos.

I'm not familiar with any specifics of IBM's implementation but from an EJB 3 spec perspective there is no need to use PortableRemoteObject.narrow() if you're retrieving an EJB 3.0 Remote Business interface, regardless of the component type( stateful vs. stateless). In addition, the "_Stub" class should never have to be part of your client programming model. That should be hidden within the vendor's implementation, if present at all.
If AuthenticationManager is the Remote 3.0 Business Interface
@Remote
public interface AuthenticationManager {
your client lookup should be :
AuthenticationManager am = (AuthenticationManager) context.lookup("...");

How to typecast Object Class object dynamically

Hai every one
i have a object of any particular class , but i don't know the variables in that class object. But i have string variable contains value of variables in that class object.
So i use following method for get value of variables in that class object.
class ObjectCLass
     Sub s=new Sub();
     public static void main(String[] args)
          ObjectCLass a=new ObjectCLass();
          try
               System.out.println(*a.getClass().getDeclaredField("s").get(a)*);
          catch(Exception e)
               System.out.println("Exception");
class Sub
     int i=5;
     public void print()
          System.out.println("Hello World!");
}Here the bolder line give Object class object. By using this Object class object i need access the variable i and method print(). So i need to cast Object class object into sub class
so how can i typecast it
i try with following methods , but i cant succeed
1.( *(a.getClass().getDeclaredField("s").get(a).getClass)*   a.getClass().getDeclaredField("s").get(a)   ).print() ;
2.( (Class.forName(�Sub�) ) a.getClass().getDeclaredField("s").get(a) ).print();Please any one one help me how to typecast it dynamically
By
Thiagu

If you know you're going to invoke the "print" method on an object, then you also need to know the type of the class, or interface, which has that method.
It seems what you are looking for is a tutorial on interfaces.
http://java.sun.com/docs/books/tutorial/java/IandI/index.html
In a nutshell, you can set up an interface which defines a "print" method, and create class(es) which implement that interface. Then as long as you have an object which implements that interface, but do not know the exact type of that object, you can simply cast it to the interface type and invoke the method.

Casting the Object dynamically

Hi All,
I am looking for a way to dynamically cast the object. I am receiving an object which is JAXB object as parameter of a method. This object can be type pf one the 5 jaxb objects my logic is handling. I need to identify the actual type of object and perform some operations on it.
Each of these 5 JAXB objects have some common method (although these objects does not inherit from any common class) and some methods which are specific to them.
I can not make changes to JAXB classes as i am importing those as jar.
I know it will need reflection somehow but i am not sure how to do it exactly. Below code will give you idea what i am trying to achieve. Its giving compile time error as xngEvent is typecasted in if-else block. This is just to show what i want to achieve using reflection.
public void processMessage(Object inputObject)
if(inputObject instanceof com.att.granite.jaxb.xngevents.dtd.equipment.XngEvent){
                    com.att.granite.jaxb.xngevents.dtd.equipment.XngEvent xngEvent = (com.att.granite.jaxb.xngevents.dtd.equipment.XngEvent)inputObject;
               }else if(inputObject instanceof com.att.granite.jaxb.xngevents.dtd.cable.XngEvent){
                    com.att.granite.jaxb.xngevents.dtd.cable.XngEvent xngEvent = (com.att.granite.jaxb.xngevents.dtd.cable.XngEvent)inputObject;
               }else if(inputObject instanceof com.att.granite.jaxb.xngevents.dtd.ipaddress.XngEvent){
                    com.att.granite.jaxb.xngevents.dtd.ipaddress.XngEvent xngEvent = (com.att.granite.jaxb.xngevents.dtd.ipaddress.XngEvent)inputObject;
               }else if(inputObject instanceof com.att.granite.jaxb.xngevents.dtd.ipsubrange.XngEvent){
                    com.att.granite.jaxb.xngevents.dtd.ipsubrange.XngEvent xngEvent = (com.att.granite.jaxb.xngevents.dtd.ipsubrange.XngEvent)inputObject;
               }else if(inputObject instanceof com.att.granite.jaxb.xngevents.dtd.path.XngEvent){
                    com.att.granite.jaxb.xngevents.dtd.path.XngEvent xngEvent = (com.att.granite.jaxb.xngevents.dtd.path.XngEvent)inputObject;
               }else{
                    com.att.granite.jaxb.xngevents.dtd.site.XngEvent xngEvent = (com.att.granite.jaxb.xngevents.dtd.site.XngEvent)inputObject;
String database = xngEvent.getDatabase();
String elementType = xngEvent.getElementType();
String editOperation = xngEvent.getEditOperation();
validateEvent(elementType,editOperation,xngEvent);Thanks,
Aashu

What you are talking about is called runtime class working. It can do the job you want but for reasons the other responders already mentioned I cannot recommend it for your use case. The primary reasons being the complexity involved, the likelihood that you will need changes that will not be backward compatible, the difficulty in testing and debugging and the difficulty in finding developers that will even understand this approach that can take over after you are gone.
This type of functionality is very roughly related to the use of dynamic proxies and code injection used by Spring and other frameworks.
With those caveats in mind this is a link with an excellent example of how to do it and the issues involved.
http://www.ibm.com/developerworks/java/library/j-dyn0610/
For your use case I would recommend the approach you have probably already settled on. But first follow gimbal2's advice and document your requirements and use case and the dependencies on possibly duplicated code sections you previously mentioned.

ClassCastException - While type casting Home object after EJB JNDI Lookup

Sun One Application Server throws a ClassCastException when I try to type cast Home object to it's respective interface type.
Here is the code ---
==============================================
Object obj = PortableRemoteObject.narrow( context.lookup( jndiName ), homeClass);
System.out.println("Remote Object - obj : "+obj);
if (obj != null) {
   System.out.println("obj.getClass().getName() : "+obj.getClass().getName());
   System.out.println("obj.getClass().getSuperclass() : "+obj.getClass().getSuperclass());
   Class[] interfaces = obj.getClass().getInterfaces();
   if (interfaces != null) {
      for (int count = 0; count < interfaces.length; count++) {
         System.out.println("interfaces[ " + count + " ].getName() : " + interfaces[ count ].getName());
}==============================================
The class name is dislpayed as the Stub class name.
While displaying the interfaces, the Home Interface name is displayed.
But later when I try to type cast it into Home Interface type, it throws a ClassCastException.
Can somebody please check this?

Please post the stack trace. Also, take a look at our EJB FAQ to make sure you're doing the
recommended lookup :
https://glassfish.dev.java.net/javaee5/ejb/EJB_FAQ.html

Re-casting of object from control reference

I feel like this question is likely answered elsewhere, but after days of searching I couldn't find an answer. Sorry if I'm missing the answer in some obvious place.
I'm given a reference to a cluster control and told that the elements of the cluster are all children of parent class A. Using the controls[] property I get an array of the elements, and the value property of each of those elements gives a variant that can be turned into class A. At that point, all of the object oriented overriding and private data stuff works as expected.
So far so good.
But one method I call on those objects changes the private data, and I need to update the control with the updated object. There I get a runtime error because the control isn't A but some child class of A.
I think this is where Preserve Runtime Class comes into play, but since I only get a reference to work with, what do I do? This is especially frustrating because debugging probes show that LabVIEW knows the child class on the wire, but I can't see how to tell LabVIEW to cast down to the class that it knows it has.
For example, is there some way to use the ClassName property of the control to cast the object of class A into the child that the control is expecting?
Solved!
Go to Solution.

nathand wrote:
So your trying to write to the specific control within the cluster, by reference, as a variant, and you're getting an error? What's the actual text of the error?
Really you shouldn't ever be using a front panel object this way, especially one where the user never sees the data in it. For passing data around you should use a wire. Neither a wire nor a DVR will get you the ability to pass an arbitrary cluster, though, which it sounds like is what you're trying to do. With a bit more information we might be able to suggest a better approach.
I don't have the text of the error handy, but it comes from the write value property node and basically says the given variant can't be converted to the type of the control. It happens only when the value is cast to the parent class, which makes sense.
In other words, given a control of child type,
control.value ---> variant ---> to parent ---> variant ---> control.value failes with the error
control.value ---> variant ---> to child ---> variant ---> control.value succeeds
So a solution would be a way to cast to the child instead of to the parent. LabVIEW knows what class the control contains; it is listed in a number of places from the ClassName property through the probe window. The problem is I know of no way to bridge the gap from "LabVIEW knows what class this thing is" to "have LabVIEW cast the variant to that class."
I completely agree that I shouldn't have to ever be using a front panel control this way, but I don't want to get sidetracked into talking about the shortcomings of LabVIEW that have required such a use. Suffice it to say, that is the assignment.

Create array of arbitrary dimensions / get Class object for primitive types

Here's an interesting problem: is there any way to code for the creation of an n-dimensional array where n is only known at runtime (input by user, etc.)?
java.lang.reflect.Array has a newInstance method which returns an array of an arbitrary number of dimensions specified by the int[] argument, which would give me what I want. However, the other argument is a Class object representing the component type of the array. If you want to use this method to get an array of a primitive type, is it possible to get a Class object representing a primitive type?

That doesn't help, since the whole problem is that the number of dimensions aren't known until runtime. You can't simply declare a variable of type int[][] or use an int[][] cast, since the number of []'s is variable.
The int.class construction was partly what I was looking for. This returns the array needed (assuming some read method):
int dimensions = read();
int size = read();
int[] index = new int[dimensions];
for (int i = 0; i < dimensions; i++)
index[i] = size;
Object myArray = Array.newInstance(int.class, index);The only problem is, as an Object, I can't use myArray usefully as an array. And I can't use a cast, since that requires a fixed number of dimensions.

Casting - Class.cast() anyone?

Hi,
I try to cast an object to a class which I don't know excatly at compile time. I think, Class.cast() is made for that. However, it won't compile and I don't know why.
Here is some sample code for reproducing my problem:
        JComponent thing = new JButton();
        Class thingClass = Class.forName("javax.swing.JButton");
        thingClass.cast(thing).setText("blurb");this yields:
test.java:11: cannot find symbol
symbol : method setText(java.lang.String)
location: class java.lang.Object
        thingClass.cast(thing).setText("blurb");so Class.cast() returns an object, but (at runtime) this is an instance of a specific class. What do I miss?

The hint to go for reflection was the right thing to do. So the sample code looks now like the following (there are some exceptions to catch):
        JComponent thing = new JButton();
        Class thingClass = Class.forName("javax.swing.JButton");;
        Method methodSetText = thingClass
                .getMethod("setText", new Class [] {String.class});
        methodSetText.invoke(thing, new Object[] {"blurb",});thanks.

Casting webservice Objects

I've got a question about Webservices in Flex. When using the 'Import Web Service'-command, Flex automatically creates the appropiates Classes and Connection scripts. When using these scripts, Flex automatically casts Objects received by a Webservice to a Strong-typed Class, and not a ObjectProxy. This is very handy. The only downside of this features is that you'd have to recreate all the files when you change a property in your webservice. Because I had to make manual changes in the generated files, everytime I make a change in my Webservice, I have to update all these files again. Therefor I would like to make my own connectionscripts, so when my webservice changes, I only have to make this change in my Flex-classes. Problem is I couldn't find any scripts that correctly connects to a Webservice, AND casts my objects to a Strong-typed class. Everytime I try to cast a received ObjectProxy to a certain Class, I get null returned. I've tried several things, including the SoapDecoder, and the SchemaRegister, but I somehow can't get it to work.
Does anybody has an example of a script that does this job or know how to get this done?
Thanx,
Paul

Hi Mike,
Thank you for your response. Yes, I was trying to cast the elements returned from
examineHeaderElements to SOAPHeaderElement. This was throwing a ClassCastException.
Now, I am using
soapHeader.getChildElements(nodeName)
This seems to work fine. Where I created the nodeName through SOAPEnvelope's createNode()
method. Don't know what the original problem was. But, now I avoided using that
API. Will let you know if I get any more information.
Regards,
Adam
"Michael Wooten" <[email protected]> wrote:
>
Hi Adam,
The java.util.Iterator returned from the examineHeaderElements() method,
should
contain javax.xml.soap.SOAPHeaderElement objects. Is that what you are
trying
to cast to?
Regards,
Mike Wooten
"Adam Athimuthu" <[email protected]> wrote:
Hello,
I am getting a ClassCastException when trying to process the SOAPHeader
in a SOAP
handler. I tried the following...inside the handleRequest(MessageContext
context)
method:
SOAPPart soapPart=null;
SOAPEnvelope soapEnvelope=null;
SOAPHeader soapHeader=null;
SOAPMessageContext soapContext=(SOAPMessageContext) context;
System.out.println("handleRequest");
SOAPMessage soapMessage=soapContext.getMessage();
System.out.println("SOAPMessage: "+soapMessage.toString());
try
soapPart=soapMessage.getSOAPPart();
soapEnvelope=soapPart.getEnvelope();
soapHeader=soapEnvelope.getHeader();
System.out.println("SOAPHeader: "+soapHeader.toString());
soapHeader.addTextNode("CustomNode");
Iterator allHeaders=soapHeader.examineHeaderElements("http://someuri.com");
The examineHeaderElements throws a ClassCastException, no matter what
method gets
invoked on the soapHeader object. I tried casting this to the weblogic.webservice.core....
implemented objects. The result is the same.
I appreciate any help.
Thanks,
Adam
Athi D. Athimuthu

ClassCastException on casting same objects differing in canonical name

Hi all,
I have got a problem with class casting. Some years ago I comitted the error not to bundle my classes in packages and now I need to do so. Unfortunately I can't deserialize previously saved objects from files anymore using ObjectInputstream, I get a ClassNotFoundException.
file = new File(filename);
FileInputStream fos = new FileInputStream(filename);
ObjectInputStream oos = new ObjectInputStream(fos);
try
     _transaktionen = (ArrayList) oos.readObject();
catch (ClassNotFoundException e)
     JOptionPane.showMessageDialog(null, "Loading error (transaction)" +
                                        "\n"+e.getMessage());
} Finding out their serialVersionID and make it explicit does not help either, so I created a copy of the class to deserialize in a package, since I need to reference to the class, and left anotherone in the default package.
My problem now is that I can deserialize the objects, but cannot cast the object from the file to the type of the class in the package.
//getting transactions from the arraylist previoulsy loaded from the file with iterator "it"
DBFensterSeite aktuelleSeite =
                    new DBFensterSeite((Transaktion) it.next(), 1, null);Both have been loaded by the same ClassLoader, have the same serialVersionID and only differ in the canonical name (one is called Transaction, the new one is called packagename.Transaction). I am not quite sure whether this is the error, maybe you can help me. Thanks in advance!
Regards,
S�ren

>
Yes, technically you can. It does however require
that you compile the new classes using a pre 1.3
compiler. Then you just use them with the newer
compiler.You mean, in Java 1.3 it was possible to reference classes in the default package?
>
You should look into providing a migration process
however. Before installing the new application run
another application that 'reads' the old stuff and
'writes' it to a new location. That way your new
application doesn't need to deal with the old stuff
at all.Well, yes and no. The program implicitly executes a conversion on reading the file. Once you save it, it's in the new format (and thus unreadable for the old program). I do not want to provide a static conversion at installation time, because the customer, hopefully, backups data in the old format. He would not be able to read it after restoring data or, if there was something like a conversion function or program, would find it annoying having to think about it. In the end, they asked me to write the program for keeping it as simple as possible :-)
I'm quite happy about the way it works now; the new cast-methods enable me to change the data types interfaces without having to bother about anything. ;-)
Who gets the dukes now? :-p

Cast Class object

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